Burrs form at the tool exit side in the machining of metallic workpieces. These coarse burrs have to be removed prior to the further treatment of the workpieces so that no disturbances can arise in the following processes or so that no injury to the machine operators can occur. Prior to a heat treatment process, the face edges of gear teeth may be provided with a protective chamfer which is intended to protect the tooth edges of the workpiece from damage and bulging and to protect the hard fine machining tool in the following process from highly carburized hard edges and burrs. The term deburring is in this respect frequently used synonymously for deburring and chamfering. Deburring is understood as the removal of the coarse burr which adheres to the workpiece after a metal cutting process, and chamfering is understood as direct application of a protective chamfer. In this way, rough burr is removed in so doing depending on the process.
In the large-scale production of gear cut workpieces with diameters smaller than approx. 500 mm, a chamfering and deburring of gear cut workpieces in a gear cutting machine have become part of the art. One example process for this includes pressure deburring/rotary deburring as shown in DE 25 34 574 A1. Another example process includes cutting a chamfer using special cutters (“Chamfer Cut”) as shown in DE 20 2005 014 619 A1. Still another example process includes cutting the chamfers using burrs which are pressed onto the face edges of the gear teeth at a specific angle by means of a defined preload force, so that they “roll off” the chamfer contour (“Gratomat”) as shown in DE 1 969 872 U. For smaller gear cut workpieces (<ø −500 mm) such as ones installed in small gearboxes and/or automobile and commercial vehicle gear boxes, the aforementioned chamfering and deburring processes have been used successfully for some time. In mass production, the procurement of especially adapted chamfering and deburring tools is economic since the process carried out therewith takes up little machining time. The chamfer and deburr machining predominantly takes place in such machines in parallel with the primary processing time for gear cutting. However, these tools are especially adapted to specific gear teeth but may still be used with very similar gear teeth (for example other gear widths).
With large gear teeth (workpiece diameter>1000 mm to >16,000 mm), and large modules and workpieces weighing tons, the gear cut workpieces may be machined using manually guided deburring tools, for example, using one-hand grinders. The larger the workpiece diameter and the larger the module, the more probable a manual deburr cutting is used, especially when it is a case of small workpiece batch sizes for which the procurement of a specially adapted deburring tool such as a ChamferCut machine is not economic.
With a more recent process interpretation, the trend is to move away from chamfering using manually guided deburring tools. There are various reasons for this. One reason is that demands on the gear tooth quality are increasing considerably for some gear teeth. With heavy duty gear teeth, for example for wind power gearboxes, attention is paid more and more also to reproducibility for chamfer size and chamfer angle on all teeth and workpieces and to the chamfer quality. Another reason is that the focus in the cutting of these workpieces is no longer only on the pure cutting time, but it is rather more important to obtain a workpiece from the machine which has been fully cut as much as possible. Yet another reason is that for reasons of health and safety, the manual workplaces suffering from high noise and dust emissions are no longer desired in a modern production hall. Still another reason is that blanks and gear cut workpieces are expensive especially in workpieces with large gear teeth. If a gear is strongly damaged on handling, there are in part very long replacement times until a blank is available which can be gear cut. It is therefore also attempted here by the integration of additional processes in the gear cutting machine to produce a workpiece from the machine which is as finished as possible. Further still, there may be workpieces in which end faces of the gear teeth are not planar, but which have slopes, radii or steps. In this case, in particular with helical gear teeth, the application of a uniform chamfer using manually guided deburring tools is very difficult.
Based on the aforementioned reasons, a method for automated generation of the chamfers at the front edges of the gear teeth with large gear teeth is provided. In one example, the method may provide an inexpensive solution and due to the small workpiece batch sizes, gear teeth may be able to be cut which are as different as possible. In addition, the risk that the workpiece is damaged on transport or when being chamfered may be minimized.
Separate deburring machines which are also available for large gear teeth (<3500 mm diameter) currently are not suited. These deburring machines frequently work with a system in which the cutter lies on the tooth edge and thus follows the tooth edge (Gratomat system). The disadvantage of this system is that the chamfer angle and the chamfer size over the tooth height are greatly different.
One example system works with a burr which tracks the tooth contour guided over an auxiliary device. DE 11 2008 003 992 T5 shows an independent deburring machine with two embodiments for both the chamfering and deburring of workpieces with internal teeth and with external teeth. The workpieces are in this respect guided between two workpiece holding rollers and a workpiece drive holding roller in front of the tool. The tool in this respect follows the gear tooth contour over a workpiece probe member. This kind of deburring device, is limited to chamfering of gear teeth having planar end faces of workpieces with straight gear teeth. If slopes or kinks are present in this region, the tool would have to be tracked vertically to the tooth contour in its delivery movement, which has not yet been provided in these units.
Another disadvantage of the above mentioned deburring machines is that they are independent machines having their own control, machine table for the workpiece, safety housing, etc., whereby corresponding costs are incurred. In addition, these machines require a separate installation area, which becomes very noticeable with large gear teeth. The workpiece additionally first has to be transported from the gear cutting machine to the deburring machine and has to be clamped again there, which in turn comprises an increased handling risk.
In yet another example, DE 20 2012 008 601 U1 shows a machine tool having an integrated chamfering and/or deburring device. The deburring device having numerically controlled axes is integrated with vertical adjustability and in a deliverable manner in the base region in a counter-holder stand. The limitation of this unit is it requires an additional back rest and that additionally at least three further numerical control (NC) axes have to be integrated into the machine.
In yet another example, DE 10 2009 019 433 A1 discloses a system having a separate ChamferCut deburring device for a gear cutting machine which is mounted laterally at a stand next to the workpiece table. Ideally, one of the two end faces of the gear teeth should be chamfered during the hobbing by this ChamferCut cutter. The workpiece dependence of the ChamferCut cutter, which is designed directly for specific gear teeth and which can thus be used economically in larger production runs, is disadvantageous in this method.
It is the object of the present disclosure to provide a deburring method and an inexpensive chamfering and deburring apparatus with which a chamfering and deburring, especially of large gear teeth, can take place on one gear cutting machine. The workpiece should subsequently be able to be unclamped from the machine with a completed chamfering and deburring.
This object is achieved in accordance with the present disclosure by a method for chamfering and deburring a gear cut workpiece comprising, arranging a chamfering and deburring apparatus on or at a cutting head of a gear cutting machine; and cutting a chamfer by pivoting a chamfering spindle of the apparatus with a chamfering miller from a rest position outside a disturbing contour of the gear cutting machine into a work position in a working region of a gear cutting tool at the chamfering and deburring apparatus, wherein, the chamfering spindle is positioned with the chamfering miller closer to the workpiece than the gear cutting miller so that the gear cutting tool can remain in a cutting head of a chamfer cutting; wherein movements of the chamfering spindle with a chamfering cutter for a contour tracking along the tooth edge take place by movement of axes of the gear cutting machine.
In a further embodiment the object is achieved by a chamfering and deburring apparatus comprising a chamfering spindle; a chamfering miller; a drive motor; and a control system with computer readable instructions stored on non-transitory memory. After the chamfering and deburring apparatus has been arranged on or at a cutting head of a gear cutting machine; the apparatus is used for cutting a chamfer by pivoting the chamfering spindle with the chamfering miller from a rest position outside a disturbing contour of the gear cutting machine into a work position in a working region of a gear cutting tool, wherein the chamfering spindle is positioned with the chamfering miller closer to a workpiece than a gear cutting miller so that the gear cutting tool can remain in a cutting head of a chamfer cutting; the apparatus moves the chamfering spindle to track a contour of a gear tooth edge via movement of axes of the gear cutting machine.
The apparatus in accordance with the present disclosure is mounted on or at a cutting head of a gear cutting machine. This provides the advantage that the machine axes which are first utilized for generating of gear teeth at a workpiece can also be used at least partly or even completely for the chamfer cutting.
After completing the gear cutting machining, the chamfering and deburring apparatus is moved or pivoted out of its rest position into its work position for carrying out the method in accordance with the present disclosure and the chamfer cutting is subsequently begun. The rest position of the deburring apparatus in this respect may be located on the cutting head above the tool mount for the hob or profile milling cutter for the generation of the gear teeth. Therefore, minimal disturbance is caused to the travel movements of the milling cutter head for the gear machining and the risk of collisions with the workpiece or with the apparatus for the workpiece clamping is low in the gear teeth generation process. On the other hand, the apparatus can be attached very close to the cutting point for the gear cutting machining and can thus easily be brought into engagement with the gear teeth by simple travel movements. The delivery of the deburring cutter to the gear cut workpiece in this respect takes place in a plane which extends in parallel with the X axis/Z axis and with the center axis of the machine table. In the working position, the deburring spindle is located between the gear cutting tool and the workpiece, but at least in front of the gear cutting tool. The deburring apparatus can thus be used without the gear cutting tool first having to be deinstalled from the machine. This also means that the gear teeth manufacturing process and the chamfering process can take place after one another in an automatically controlled manner and a fully cut workpiece leaves the machine. It would furthermore be possible to carry out a chamfering and deburring cutting between a plurality of milling cutting steps. This would not be possible with a necessary removal of the gear cutting milling tool.
The chamfering tool, for example a conical or cylindrical burr, is in this respect guided along the tooth edge of a gear tooth via axial movements of the cutting head with its chamfering and deburring apparatus, while the workpiece rotates at a predefined speed about its center axis. In a first step, the chamfer is first milled at an end face, for example at the upper side, of a gear tooth. Subsequently to this, the tool is delivered toward the oppositely disposed end face of the gear tooth and in a second step this end face is also provided with a chamfer. Via the pivot device for the chamfering spindle, its inward pivot angle can, for example, be controlled via the tooth height and can be varied based on the flank. A different chamfer can thus be generated on the right and left flanks and, where necessary, also at the tooth root and the tooth head.
Parameters such as the chamfer size, chamfer angle and chamfer extent can be stored in a technical program aspect in a cutting program in the machine control and can be set by the NC axes. For example, the parameters can be stored in a look-up table in the memory of a control system of the machine. The chamfer size can then, for example, also be influenced via the feed values or via the number of cuts. Controlled by the NC program, these chamfer parameters can be reproducibly generated at a plurality of workpieces.
In another example embodiment, the chamfering and deburring apparatus is still additionally mounted on a further delivery axis which extends in the radial direction toward the workpiece. A more dynamic movement in the X direction (delivery direction of the tooth height) is made possible by the lower mass to be moved, namely only the chamfering and deburring apparatus instead of the complete machine stand. Higher axial speeds can thus be traveled overall with all used axes. This is of advantage in chamfer cutting in the region of the tooth flanks since this is where the greatest changes of the radial delivery per angle degree are required at the workpiece. In the region of the tooth head and tooth root, in contrast, only small radial deliveries per angle degree are required at the workpiece.
Furthermore, it would be possible by an additional NC axis at the deburring apparatus to enable movements in parallel to the X-Z plane along the end face of the gear teeth at a higher speed since the moved mass is only composed of portions of the deburring apparatus and of the drive for the deburring tool so that the entire cutting head no longer has to be moved in the vertical direction (Z axis). The deburring apparatus may be configured differently depending on the required performance data by these different possible embodiments.
In another further embodiment, a measurement system can be arranged in the machine or at the cutting head of the machine with which measurement work may be carried out at the gear teeth. This may serve to determine and to document the gear tooth quality, but also to generate the gear teeth positioned with respect to a specific point. This measurement device may also be used in accordance with the present disclosure to determine the position of the gear teeth and the tooth shape at the workpiece and optionally also to determine the extent of the end face in the region of the gear teeth. This tooth contour thus does not have to be programmed in a complex manner, but can rather be calculated by the machine control by a simple measurement, e.g. of a single tooth gap and of the end face in the region of the gear teeth. It is sufficient in this respect if only one tooth or one tooth gap is measured. For the remaining gear, tooth contour may be calculated using gear tooth data such as the number of teeth, the tooth width, the helical angle of the gear teeth and other gear teeth data. These data are already known from the gear tooth generation and may also be entered into the calculation. A controller may then be configured with computer readable instructions stored on non-transitory memory to create a program for the chamfer cutting of the total gear teeth from this. This method can be used with involute and non-involute gear teeth. As such, the determination of the flank extent is not trivial with non-involute gear teeth.
It would equally be possible only to scan a part of a region of an individual tooth or of a tooth flank such as the tooth root and the tooth head region using the measurement device since the extent of the tooth flank is already known from the gear tooth cutting, especially with involute gear teeth. A chamfering program is thus achieved very simply and very fast without necessity of a large programming effort.
Another possibility for programming of the chamfer shape comprise a “teach-in” method, ideally user guided. Predefined reference points can be determined at a tooth gap by a probe manually traveling to predefined points, the probe being applied to the cutting head. The machine control can then subsequently also create from this, together with the gear tooth data known to the control, the cutting program for the remaining gaps. A plurality of reference points in the region of the tooth head radius and tooth root radius are important in this respect. The location of the involute along the tooth flank is very largely known by the preceding gear cutting process.
In a further example embodiment, the chamfering and deburring apparatus can also be utilized for further cutting operations at the workpiece, such as milling cutting operations, drilling operations or grinding operations. Different cutting operations can also be carried out after one another via an optionally automated tool or cutting head change at the chamfering and deburring apparatus.
Further features, details and advantages of the present disclosure will be explained in more detail with reference to embodiments shown in the figures.